1. Field of the Invention
The present invention relates to an optical coupling system comprising a light measuring device and a sample. More specifically, the present invention relates to an optical coupling system wherein a coupling lens is arranged ahead of an optical fiber and a lens portion is integrally formed at the bottom of a sample container, and excitation light, transmitted by the optical fiber, is efficiently coupled with the sample by the coupling lens and the lens portion, and an optical coupling system wherein light generated by a sample is efficiently coupled with an optical fiber by a lens portion and a coupling lens. This technology can be applied for a light measuring device, for example, that irradiates a sample with excitation light, and measures the intensity of fluorescence generated by the excited sample.
2. Related Art
As a technique that physically or chemically examines or analyzes a material, a light measuring device is available that excites a sample through the radiation of light, and measures light generated by the excited sample to obtain various data concerning the sample. Example light measuring devices are an apparatus that measures the intensity of fluorescence having a specified wavelength that is emitted by an excited sample, or that measures a transient change in fluorescence and detects a specified material or monitors a change in density, and an apparatus that measures the spectrum of fluorescence emitted by a sample to perform a quantitative or qualitative analysis. Since both apparatuses are capable of conducting highly sensitive measurements and are appropriate for the performance of microanalysis, they are widely employed. When a liquid sample is used, during the measurement process the sample is retained in a transparent sample container that permits irradiation with an excitation light and fluorescence.
For these light measuring devices, excitation light is projected onto a sample that is positioned at a location to which light from a light source is emitted, and fluorescence generated by the excited sample is appropriately collected and enters an optical detection system. Recently, another structure has been proposed wherein, using an optical fiber, excitation light is transmitted to a sample through a coupling lens, and by using another optical fiber, fluorescence output by the sample is guided through the coupling lens to an optical detection system (see, for example, JP-A-11326210). When the optical fibers are employed in this manner, the degree of freedom is increased for the positional relationships of the sample, the light source and the optical detection system. Further, since the fluorescence to be detected is transmitted through the optical fiber, disturbance light seldom enters the optical system, so that the sensitivity of an analysis of the fluorescence, which in many cases is weak, can be increased.
However, according to the conventional example, fluorescence cannot be efficiently extracted from a sample. As one reason, fluorescence output by the sample container is dispersed. As another reason, since there is a long distance between the sample and the coupling lens, it is difficult for fluorescence to be collected at the coupling lens, and since the irradiation area for excitation light is large and the radiation density is low, the surface emission of fluorescence occurs. Further, in the conventional example, a sample cannot be irradiated efficiently using excitation light. The reason for this is that since an excitation light optical fiber, that has a comparatively large diameter is employed in order to increase the intensity of the excitation light, the excitation light can not be controlled by a coupling lens and directed to a predetermined location for a sample, and thus, the radiation density of the excitation light is lowered.
Additionally, in the conventional example, since the amount of excitation light and the amount of fluorescence are increased as much as possible, an optical fiber having a large diameter, or multiple optical fibers, must be employed, and accordingly, the diameter of the coupling lens must be increased, and to connect the excitation light with the fluorescence, a plurality of lenses are required. Thus, the size of the optical system is increased.